(a) Field of the Invention
This invention generally relates to system for warning drivers of a vehicle of an approaching emergency vehicle, such as an ambulance, police car, or fire truck. More particularly, but not by way of limitation, to a device that detects the presence and approximate location of an approaching emergency vehicle and advises the driver or user on how to avoid the emergency vehicle.
(b) Known Art
Emergency vehicles, such as ambulances, police cars, or fire trucks, typically carry a loud siren and flashing lights to warn motorists and other people on the road that the emergency vehicle needs the right of way. Unfortunately, however, many private vehicles are well insulated and include stereo systems which can fill the interior of the vehicle with sound such that the siren of the emergency vehicle becomes inaudible to the driver of the private vehicle. Furthermore, today's highways and streets often include many lanes. When an emergency vehicle is traveling down one of these multi-lane roadways, it is often very difficult for the driver of the private vehicle to determine the relationship of the emergency vehicle relative to the private vehicle, such that the driver of the private vehicle can make a clear decision as to what to do to safely yield the right of way to the emergency vehicle. For example, in certain situations it may be prudent to pull over to the right of the roadway, while in other situations, it may be safer to pull over to the center or left side of the roadway. In order to make the decision of what is the safest action in yielding the right of way, it is important to know the position and direction of advancement of the approaching emergency vehicle relative to the private vehicle.
Known devices used for warning of an approaching emergency vehicle often use electromagnetic or acoustic waves to allow the emergency vehicle to communicate with the private vehicle. For example, in U.S. Pat. No. 4,747,064 to Johnston, a device which uses an electromagnetic pulse and an acoustic pulse receiver. The Johnston device uses the sound waves to determine the speed of the approaching emergency vehicle, so that the time left until the vehicles meet can then be calculated. An important limitation of the Johnston device is that it only provides information as to how much time is left until the approaching emergency vehicle and the private vehicle meet. This leaves the driver of the private vehicle guessing as to the direction of approach of the emergency vehicle. Perhaps of more importance is that, without knowing the direction of approach, the Johnston system does not help the driver of the private vehicle in deciding the direction towards which he should pull over to yield the right of way to the oncoming emergency vehicle.
Another known solution at warning about an oncoming emergency vehicle is taught in U.S. Pat. No. 4,238,778 to Ohsumi. The Ohsumi device warns the driver of the private vehicle by way of an audible signal. The audible signal intensifies or increases in volume as the emergency vehicle approaches the private vehicle. Additionally, to a system for reducing interfering sound signals within the private vehicle is also included. This system lowers the sound volume of devices such as the private vehicle's radio, fan or other noisy device within the vehicle.
Still another approach at the problem associated with warning drivers of an approaching emergency vehicle is taught in U.S. Pat. No. 3,854,119 to Friedman et al. The Friedman device is tuned to a particular radio signal which is used as a communication link between the emergency vehicle and the private vehicle. Thus the Friedman approach, like other known approaches, boosts the ability of the emergency vehicle to warn the private vehicle of the proximity of the emergency vehicle, but does not help the driver of the private vehicle in deciding on which direction to move in order to yield the right of way to the emergency vehicle.
Thus, there remains a need for an emergency vehicle warning system that alerts drivers of private vehicles that an approaching emergency vehicle is in the area. Still further, there remains a need for an emergency vehicle warning system that allows the driver of the private vehicle to determine the direction of approach of the emergency vehicle as well as helping the driver of the private vehicle to determine the safest direction to pull over to yield the right of way to the approaching emergency vehicle.